Water Quality

By Erin Bardar. Design by Robert Simmon.

No matter where you live—along the coast, in the heartland, or somewhere in between—your life is affected by water quality. Water quality issues raise many questions that are important to us all at some point or another. Is the tap water safe to drink? Will I get sick if I swim in this lake? Why are so many fish dying in the bay? Why does this water look unusual—murky, discolored, or even remarkably clear?

Perhaps one of the most important questions to ask is: How do we know when our water is healthy? To put it simply, healthy water is water that can support and sustain life. “Water quality” is a blanket term for how the physical, chemical and biological characteristics of a water sample measure up to a set of standards. Water quality can be evaluated through a number of different tests such as color, odor, temperature, acidity, bacteria content, biological diversity, and many others.

In places like Chesapeake Bay, a major water quality concern stems from nutrient loading (increased levels of dissolved nitrogen and phosphorous). As water makes its way through a local watershed (region of land that drains into a body of water) and eventually to the ocean, it is inevitably affected by how people use the land. Runoff from fertilizers applied to agricultural fields, golf courses, and suburban lawns; deposition of nitrogen from the atmosphere; soil erosion; and discharge from aquaculture facilities and sewage treatment plants all contribute to increasing nutrient content in coastal waters.

Water Contamination
Water contamination stems from a variety of land-based sources. Image courtesy NOAA Center of Excellence for Great Lakes and Human Health.

More than 150 rivers and streams feed the Chesapeake Bay watershed. Over the last several decades, more and more land in the watershed has been converted from forest to farms, cities, and residential suburbs. This development has brought with it an increase in the land area covered by hard surfaces like roads, sidewalks, parking lots, and rooftops in places where nutrient-rich water was once absorbed and filtered by soil and plants. Higher-yield agricultural practices have also played a role in contributing increased amounts of nutrients to rivers and streams in the watershed during this time. “Dirty” water now flows, largely unfettered, through the watershed, which has led to an overabundance of nitrogen and phosphorous in the Bay. Algae (also known as phytoplankton) in the water feed off these nutrients and can bloom in excess when nutrient concentrations get too high. These algae are the base of the marine food chain and are essential to the health and productivity of the oceans. However, when they are overfed, they can do more harm than good. Algal blooms can prevent sunlight from reaching the bottom of the bay, resulting in a loss of aquatic vegetation and disruption of animal habitats. Decomposing algae can deplete dissolved oxygen in the water to dangerously low levels. This process, known as eutrophication, can result in fish kills and suffocation of other marine life. If enough oxygen is removed from the water, the area becomes a “dead zone,” where no aquatic life can survive.

Satellite image of the Chesapeake Bay.

Satellite image of the Chesapeake Bay. (NASA image courtesy MODIS Rapid Response Team.)

In the 1970s, Chesapeake Bay developed one of these dead zones. Fortunately, dead zones are reversible. By monitoring local water quality, key sources of nutrients can be identified and actions can be taken to ensure that harmful nutrient loading is reduced. Today, Chesapeake Bay continues to struggle to recapture its health, and remains on the Environmental Protection Agency’s “dirty waters” list. Read Drought and Deluge Change Chesapeake Bay Biology to find out how Chesapeake Bay resident and NASA scientist Jim Acker was able to identify links between nutrients and water quality in Chesapeake Bay.

How Citizen Scientists Can Meaningfully Contribute Using Their Own Observations

The benefits of water quality monitoring have been likened to those of visiting your doctor for periodic checkups. Observing trends over time can help avoid major health problems or readily identify them when they do occur. Bodies of water in the United States are monitored not just by state, federal, and local agencies, but also by universities and volunteers.

University or government-funded scientists typically monitor water quality at the mouth of major river systems, but they do not have enough resources to track water quality through every river and stream in a watershed. This makes volunteers and citizen scientists vitally important in the effort to monitor and maintain water quality standards across the nation.

Citizen scientists can meaningfully contribute by monitoring water quality (including nitrogen concentration) in a nearby river, lake, or stream, and identifying potential sources of pollution in their local and regional watersheds. This can significantly increase the amount of water quality data available to government agencies for bodies of water that may otherwise go unassessed. A network of citizen scientists can potentially monitor an entire watershed. This type of grass-roots science has great potential for identifying local sources of contamination, which could ultimately be used to reduce a community’s impact on the ocean.

How Citizen Scientists Can Meaningfully Contribute Using Satellite Data

With the help of watershed maps, the paths of streams and rivers can be traced to the ocean. Citizen scientists can then tie their local water quality observations to marine phytoplankton blooms observed by NASA satellites, and identify potential dead zone locations. Although dead zones cannot be directly identified from space, algal blooms can be tracked by monitoring chlorophyll concentrations in surface waters. By looking at variations in chlorophyll levels over time, citizen scientists can determine if relationships exist between local events in their own watershed and phytoplankton blooms in the ocean. For example, a citizen scientist in Missouri or Iowa might monitor the Gulf of Mexico near the mouth of the Mississippi River and note that ocean chlorophyll levels increase about two weeks after nitrogen levels spike in their local river. By correlating satellite observations with a unique network of ground observations, a new understanding of the dynamics that drive phytoplankton blooms may emerge in the scientific community.

Exploring Nitrogen in Your Local Watershed

Testing for nitrogen in your local watershed can help identify potential “hot spots” in your community that may be contributing to nutrient loading downstream. With a simple, inexpensive field test kit, you can detect inorganic forms of nitrogen readily available to plants such as nitrate (NO3−), nitrite (NO2−), and ammonium (NH3). Before going out into the field, plan when to sample. For example, if you want to test the effect of crop fertilization on the nitrogen levels in a stream adjacent to a local farm, you’ll need to schedule your sampling according to the farm’s fertilization schedule and after a substantial rainfall. You may also want to sample the same location during a time of relatively low water flow and compare it to a sample from the same location at a time of higher water flow. The number of samples you collect and how often you collect them depends on your interests and the question(s) you have about your local watershed.


  • nitrogen (nitrate/nitrite/ammonium) test strips, available from most pet supply stores in the aquarium test equipment section or from science supply companies/as part of full water quality testing kit; (Select online retailers: Omega, Industrial Test Systems, Inc. ($15.99), Hach ($15.89)
  • water collection bottles such as Hach 250 mL Polyethylene collection bottles ($43.55 for 12 pack). Small Nalgene bottles from an outdoor supply store also work well, $2-$5 from Nalgene.
  • Internet connection
  • Google Earth (download here; latest available version is recommended)
  • The Citizen Scientist’s Guide to Earth Observations Water Quality Data Entry Sheet
  • rubber gloves (optional)
  • rubber boots (optional)
  • bucket (optional)
  • rope (optional)

WARNING: Always keep safety in mind when collecting water. If you are collecting water from the edge of a stream, river, or lake, walk carefully along the bank so as not to fall in. For safety, you can also attach a rope to bucket, toss the bucket into the water away from the edge, and bring a water sample back to shore for testing. Do not collect samples in a severe storm or flood or if there is a threat of lightning in the area. Bring a partner when possible, especially if you are planning to collect samples from water in remote areas. If you think your water source is highly polluted or might contain raw sewage, wear rubber boots and rubber gloves to avoid direct contact with the source.

CAUTION: Some experts recommend that you wear rubber boots and gloves to avoid contamination of the water sample. Rinse collection bottles in the water source you are testing to decrease sample contamination.


  1. Follow these step-by-step instructions for identifying and exploring your watershed in Google Earth.
  2. With your watershed map open in Google Earth, identify one or more bodies of water in your area from which you would like to collect samples. Choose locations that are publicly accessible or ones at which you have explicit permission from the land owner to collect samples and perform water quality tests.
  3. Place the cursor over your chosen sampling site and write down the latitude and longitude that appears in the bottom left corner of the Google Earth window.
  4. Print copies of the Water Quality Data Entry Sheet to bring with you into the field. Use this data entry sheet to keep track of all your notes and observations to make it easy to share your data with others.
  5. Go to your sampling location. Write down the date, time, and weather. Carefully note and record landmarks or other identifying features near the location in enough detail that you will be able to find the exact same location again for more observations at a later date. If you have a camera, take a picture to help you keep a record of the location and conditions.
  6. Take detailed notes about the condition of the stream or river. What color is the water? Are there any detectable odors? Is the stream/river bottom silt or rock? Are there any visible drainage pipes nearby? NOTE: It is important to be consistent and uniform when taking notes about your data collection so that it is easy to compare your observations between sampling sites and with those made by other scientists.
  7. Take detailed notes about the conditions along the stream/river bank. Is the bank rock or mud? Is it steeply sloped? Are there plants along the bank? If so, what kind are they and how far are they from the water’s edge?

    NOTE: Some plants can slow runoff and limit the amount of nitrogen that enters water at a particular location because they absorb the nutrients for themselves. However, if a body of water borders a field of crops or a lawn, excess nitrogen from fertilizers may make its way into the they were all written by different people, water. Taking careful notes about the conditions around the stream or river may help you determine the source of nitrogen and why nitrogen levels vary over time.

  8. Label your sample bottle with the date, time, and location so that you can easily identify it later.
  9. Rinse the bottle in the stream.

    CAUTION: If you do not rinse the collection bottle, the sample may be contaminated and you will not get accurate results with your nitrogen tests.

    WARNING: Be extremely careful when collecting your water sample—the stream/river bank may be slippery. Do not take samples when the National Weather Service has issued a severe storm or flood warning for the region in which you are collecting your sample.

  10. Fill your sample bottle(s) with water from the stream or river. If the water is shallow, be careful not to scrape the bottom. If you take more than one sample at a given location, make sure they are clearly and distinctly labeled. For example, if you want to test the same stream or river along opposite banks, label one bottle “east bank” and the other “west bank.”
  11. Test your sample on-site or bring the collection bottles home for testing. Samples can be refrigerated and tested the following day, but should not be stored for more than 24 hours to ensure the most accurate results. Follow the directions on the test strip kit to record the nitrate and nitrite levels of your water sample. If you do not test the sample immediately, swirl the contents of the collection bottle around before testing to ensure that the water is evenly mixed.
  12. Record the nitrate and nitrite levels for each sample in units of ppm, as well as the uncertainty indicated by the test strip manufacturer. If your tests show nitrogen levels that are considered to be out of the ordinary range (see Interpretation section below), and the source of the nitrogen is not easily identifiable at your sampling location, consider driving upstream to investigate where the origin might be.

Interpretation of results:

Nitrogen test strips are convenient, inexpensive and relatively accurate compared to commercial laboratory analysis. A typical test strip will measure nitrate levels from 1 to 50 parts per million (ppm) and nitrite levels from 0.15 to 3.0 ppm. Any concentration of nitrates in a water source may be cause for concern. If nitrate levels are greater than 10 ppm, you should not drink the water. While there are no national or state standards in place regarding nitrate levels as they relate to aquatic life, the consequences of high nitrate levels can be quite serious. Nitrate is not toxic to plants or animals, but can become toxic during digestion if it is converted to nitrite that binds with hemoglobin and prevents blood from carrying oxygen. High levels of nitrates can also result in increased plant and algae growth in water, which can lead to hypoxia (decreased oxygen). If dissolved oxygen levels in the water get low enough, fish and other aquatic life that require oxygen can die. Bodies of water with oxygen levels too low to support life are known as “dead zones.”

Water should not be consumed if nitrite levels are above 1 ppm. As mentioned above, nitrite can be extremely harmful to both humans and aquatic life. High levels of nitrite are uncommon in water because it is often rapidly converted to other nitrogen compounds such as nitrate, nitrous oxide or nitrogen gas through chemical reactions.

The nitrogen you might detect in the water comes from a variety of sources. Some stems from natural rock or soil deposits, but the majority of it comes from things like wastewater treatment plants, septic systems, and runoff from fields and lawns. For more information about nitrates and nitrites in drinking water, take a look at the EPA’s Consumer Factsheet on Nitrates/Nitrites. To learn more about the ill effects of excess nitrogen on aquatic life, read the Scientific American article Oceanic Dead Zones Continue to Spread.

Going Further

If your research interests are focused on nitrogen contributions to your local water source from runoff, you should consider rainfall when making your observations. Runoff samples will be most revealing after a significant rainfall. To make a quantitative assessment of the relationship between nitrogen levels and rainfall, you will need to collect time series rainfall data from your sampling site. For step-by-step instructions about how to collect rainfall data, see the Precipitation chapter of this guide.

You might also want to test your water sample(s) for other nutrients. In addition to nitrogen, compounds containing phosphorous are also commonly found in fertilizers that make their way into water through runoff. Phosphates can cause algae blooms, which like nitrogen, can lead to hypoxic conditions and dead zones. To test for phosphorous, you will need a phosphate test kit. Like nitrogen test kits, these kits are relatively inexpensive and available from most pet supply companies in the aquarium testing section. Follow the nitrogen testing procedures and any additional manufacturer instructions to test your water sample(s).

For additional water quality monitoring ideas, visit NASA’s Goddard Earth Sciences Data and Information Services Center (GES DISC) Amateur Scientist’s Guide to Water Quality Monitoring Observations. This site has instructions for monitoring a variety of water properties including turbidity, salinity, dissolved oxygen, pH, temperature, and hydraulic flow.

Monitor chlorophyll concentrations near major river systems connected to your watershed.


Nutrients such as nitrogen and phosphorous are not directly measurable with satellite observations. However, satellites can measure chlorophyll concentration, which can act as somewhat of a proxy for nutrient loading in bodies of water.

An algal bloom is a rapid increase in the population of algae or phytoplankton in an aquatic system, and can be recognized by discoloration in the water. The discoloration arises from the presence of chlorophyll, a green pigment used for photosynthesis. Because phytoplankton contain chlorophyll, the distribution and abundance of phytoplankton in oceans, lakes, and seas can be determined through satellite measurements of chlorophyll concentration.

Micrographs of algae.
Microscopic view of tetraselmis algae. ©2004 Food and Agricultural Organization of the United Nations (FAO).

When marine algae are overfed with excess nutrients, their reproduction rates can increase significantly. Fertilizer containing these nutrients can find its way into lakes and oceans through runoff from agricultural farms, golf courses, and suburban lawns. Other nutrients get added from the atmosphere, soil erosion, upwelling, aquaculture facilities, and sewage plants. Try this simple experiment at home to see for yourself how the nutrients in fertilizers can trigger algal blooms.

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is an instrument on the Orbview-2 satellite that monitors ocean characteristics like chlorophyll a concentration and water clarity. Using images and data from SeaWiFS, you can look for evidence of algal blooms and compare your findings with your backyard observations to see if there are any correlations between high levels of chlorophyll and sources of nutrients upstream in your watershed.

Nutrients from both point (single, identifiable sources) and nonpoint sources contribute to changing chlorophyll a levels in Chesapeake Bay. The step-by-step instructions below describe how to use Giovanni to explore monthly chlorophyll concentration, using Chesapeake Bay as an example. A very dry month (April 2002) and a very wet month (April 2003) were chosen to show how chlorophyll concentration in the Bay is affected by upstream conditions in the Chesapeake Bay watershed. These different conditions caused very apparent changes in the biological properties in the waters of the Bay and along the coast. During the wet month, there was increased water flow to the Bay. This led to increased runoff throughout the watershed and resulted in higher concentrations of nutrients reaching the Bay. You can adapt the procedures outlined here to study the mouth of your own watershed.

NOTE: All of the same operations described in this example can be performed with ocean color/chlorophyll data from the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument aboard NASA’s Aqua satellite. As the youngest of NASA’s ocean color instruments, MODIS-Aqua is likely to be the sensor of choice for 2010 and beyond.


  • Internet connection


  1. Go to the Giovanni Ocean Color Radiometry Online Visualization and Analysis Global Monthly Products site to access the data. Click here for help with Giovanni functions.
  2. Click and drag your mouse on the map to select your area of interest. Use the zoom and pan tools at the top left of the map window to help locate the exact region you want to study. Redraw the selection box as necessary. You can also enter latitude and longitude coordinates in the appropriate boxes to set the boundaries of your selection box on the map.

    Screenshot of giovanni selection interface.
  3. Scroll down and select SeaWiFS Chlorophyll a concentration in the Parameters box.

    Screenshot of Giovanni parameter selection interface.
  4. Choose the Time Period: Begin Date: Year 2002, Month - April; End Date: Year 2002, Month - April. Leave the visualization type as Lat-Lon map, Time-averaged. And click the Generate Visualization button.

    Screenshot of giovanni date selection.
  5. Scroll down to the Edit Preferences box below the chlorophyll map and adjust the color bar settings. Click the radio button for Custom and enter a minimum value of 0.5 and a maximum value of 10. Then click the Submit Refinements button to refresh the page.
  6. Examine the resulting visualization. Chlorophyll concentrations are measured in milligrams per cubic meter (mg/m3). As the legend shows, red areas contain the greatest concentration of chlorophyll (and therefore the greatest concentration of phytoplankton), while the purple areas have very low chlorophyll concentrations. It is important to note that chlorophyll concentrations measured by satellite are less accurate near the coast (particularly in shallow waters) than they are farther offshore, but the measurements are still useful for observing changes in water quality.

    Chesapeake Bay chlorophyll concentration, Aprill 2002.
  7. Change the Time Period to April of 2003 and generate a new visualization.

    Chesapeake Bay chlorophyll concentration, April 2003.
  8. Try looking at how chlorophyll concentrations in the Chesapeake Bay region (or some other region of your choice), change over the course of a year. Go back to the main Giovanni page and select your area of interest and the SeaWiFS Chlorophyll a concentrationparameter as you did before. This time, set your start and end dates to cover one year (e.g., January-December, 2007). Instead of choosing the Time-Averaged Lat-Lon map, choose Animation as your visualization type and then click Generate Visualization. NOTE: Due to technical difficulties with the SeaWiFS instrument, which have since been remedied, there are a few months of missing data in the first part of 2008. If you would like to explore chlorophyll concentration for this time period, use MODIS-Aqua data instead.

    Screenshot of Giovanni visualization type.
  9. Use the control buttons at the bottom of the player window to watch the animation. Look for evidence of seasonal changes and periods of relatively high or low chlorophyll concentration.

    Giovanni animation player.

Consider the following questions for both the Chesapeake Bay and your own watershed: What correlations are there, if any, between high levels of chlorophyll concentration and nutrient levels upstream? What kinds of events might be responsible for changes in chlorophyll concentration over time? What are some ways to control the amount of nutrients being delivered to coastal waters from these types of pollution?

NOTE: Because just a few days of elevated chlorophyll signals will typically dominate a monthly average, monthly data should be sufficient for identifying blooms and events. However, if you want to explore chlorophyll data at a higher temporal resolution to get a better sense of the timing surrounding a particular event, you might consider exploring SeaWiFS 8-Day data.

Going Further: Exploring Dead Zones

Dead zones are a growing problem around the world. Over the last 40 years, the number of identified dead zones has risen from less than 50 to over 400. Millions of tons of food and millions of dollars are lost each year as a result of hypoxic events. In the Chesapeake Bay dead zone alone, more than 83,000 tons of fish and other aquatic organisms fall victim to hypoxia every year. According to the August, 2008 Scientific American article Oceanic Dead Zones Continue to Spread, excess nitrogen is the primary cause for this global crisis.

Dead zones layer in Google Earth 5.

Google Earth 5.0 has a new ocean layer that includes data on marine dead zones. To turn on the dead zone locations, first expand the Ocean layer options. Then, expand the State of the Ocean options and check the box for Dead Zones.

The location of each dead zone is identified by a skeletal fish icon. Click on the fish to get data on the nature and size of the dead zone, the date it was first observed, its impact on fisheries and deep-water ecosystems, and a reference.

Screenshot of Chesapeake Bay dead zone in Google Earth.

To find out if a river in your watershed flows into the ocean next to one of these dead zones, open the USGS Elevation Derivatives for National Application (EDNA) Derived Watersheds for Major Named Rivers and find your local watershed. If you did not already download these maps for the Backyard Investigation, download them now from the USGS EDNA Watershed Atlas site.

Take a look at the Chesapeake Bay dead zone or any other dead zone of interest to you. Try navigating upstream (or up current) from these dead zones to see if you can figure out which land areas polluted freshwater might be coming from. As an example, the major source of water to the upper Chesapeake Bay is the Susquehanna River, which flows through much of the rich agricultural region of central Pennsylvania. If you would like to explore additional ocean data related to nutrient loading and dead zones, go to the Google Earth Ocean Gallery and download the World Resources Institute EarthTrends kml file, which displays areas that are eutrophic (characterized by excess nutrients) and hypoxic (low levels of oxygen), as well as improving hypoxic zones and naturally hypoxic zones where low oxygen levels are a result of seasonal changes in ocean currents and upwelling.

Consider your backyard observations in your local watershed, your Earth observations of ocean chlorophyll concentrations, and your Google Earth exploration of dead zones. Are you able to find any compelling evidence that land use practices in your local watershed might be having a negative impact on the ocean?

Backyard Observation Supplies

  • nitrogen (nitrate/nitrite/ammonium) test strips, available from most pet supply stores in the aquarium test equipment section or from science supply companies/as part of full water quality testing kit; (Select online retailers: Omega , Industrial Test Systems, Inc. ($15.99), Hach ($15.89)
  • water collection bottles such as Hach 250 mL Polyethylene collection bottles ($43.55 for 12 pack). Small Nalgene bottles from an outdoor supply store also work well, $2-$5 from Nalgene.
  • Internet connection
  • Google Earth (download here; latest available version is recommended)
  • The Citizen Scientist’s Guide to Earth Observations Water Quality Data Entry Sheet
  • rubber gloves (optional)
  • rubber boots (optional)
  • bucket (optional)
  • rope (optional)

Earth Observation Supplies

  • Internet connection

Earth Observation Data Sheet

References and links to background material like science papers and popular science articles on the topic.

The power of citizen science is in sharing your observations with others who are making the same observations in other place. The network of measurements provides a larger picture of air quality than any single person could gather alone.

To share your data with others around the country who are making similar observations, go to Volksdata. [http://www.volksdata.com]

Your First Visit

  1. The first time you visit, you will have to register for the site.
  2. Click on “Register For A New Account” link on the right hand side of the page and follow the instructions.
  3. Sign in with your new username and password, and then click on “Join an existing program.”
  4. Join the CARSON program. You can search for CARSON in the second box titled “Search for Projects”. If you search by metatags, type in: Carson.
  5. The CARSON program is divided into smaller projects. Please click on the project in which you plan to participate: air quality, water quality or precipitation. Each section is treated as a separate project to make it easier for data entry. You may join more than one project or section.
  6. Click on “Request Membership in this Project”. You should receive an e-mail indicating your membership acceptance into the project within 24 hours. Please do this for each project/section that you plan to participate in.

To Enter in your Observations

  1. Log in to Volksdata. [http://www.volksdata.com]
  2. Select CARSON (It should appear under Program Name)
  3. Select the chapter and project of CARSON that you are participating in.
  4. Click on New Observation. This will take you to the Data Entry sheet similar to the sheet you used in the field. Please enter in your observations here.
  5. Once you are finished entering your observations, click on “Submit- Done”. Your observations are now apart of the global CARSON data set.
  6. Click on “View Project Data” to view the entire set of observations.

    Note: If you have additional data to enter for another project, please go back to the CARSON program and click on the next project to access the data entry form.

Air Quality- You will be able to click on any observation on the map and see the most current data for that location. You can also look back at archived data for that location to observe how one location has changed through time. Also, you can map visibility, AQI, ozone levels, Aerosol Optical Depth, and cloud cover across all of the observed locations to get a good picture of air quality changes across the entire region. This data-sharing capability can be a useful tool to the citizen scientist who is interested in tracking large-scale patterns of pollution.